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    <title>Document</title>
</head>

<body>
    <div>
        <h2>Promise 封装 AJAX请求</h2>
        <button class="btn">请求</button>
    </div>
</body>
<script>
    // 地址:https://api.uixsj.cn/hitokoto/get?type=social

    const btn = document.querySelector('.btn')
    btn.addEventListener('click', function () {
        const p = new Promise((resolve, reject) => {
            // 1.创建AJAX对象
            const xhr = new XMLHttpRequest()
            // 2.初始化
            xhr.open('GET', 'https://api.uixsj.cn/hitokoto/get') 
            // 3.发送
            xhr.send()
            // 4.处理响应结果
            xhr.onreadystatechange = function () {
                if (xhr.readyState == 4) {
                    if (xhr.status >= 200 && xhr.status < 300) {
                        resolve(xhr.response)
                    } else {
                        reject('失败了')
                    }
                }
            }
        })
        p.then(value=>{
            console.log(value);
        },(reason)=>{
            console.log(reason);
        })
    })
</script>

</html>